docs: def common(self, other):
          """
          Return two objects with the same dimensions if they lie in the same orthogonal plane.
          ::
  
              >>> l = Location(pop=1, snap=2)
              >>> m = Location(crackle=1, snap=3)
              >>> l.common(m)
              (<Location snap:2 >, <Location snap:3 >)
          """
          selfDim = set(self.keys())
          otherDim = set(other.keys())
          dims = selfDim | otherDim
          newSelf = None
          newOther = None
          for dim in dims:
              sd = self.get(dim, None)
              od = other.get(dim, None)
              if sd is None or od is None:
                  # axis is missing in one or the other
                  continue
              if -_EPSILON < sd < _EPSILON and -_EPSILON < od < _EPSILON:
                  # values are both zero
                  continue
              if newSelf is None:
                  newSelf = self.__class__()
              if newOther is None:
                  newOther = self.__class__()
              newSelf[dim] = self[dim]
              newOther[dim] = other[dim]
          return newSelf, newOther